That is a current full dress jacket for a private in the Grenadier Guards. The clues are the grenade on the collar, the badge on the epaulettes and the row of single buttons down the front. The Guards infantry regiments are distinguished by, amongst other things, the way the jacket buttons are arranged,:1. Single buttons-- Grenadiers.2. Double buttons--Coldstream 3. Buttons in threes -Scots Guards4. Buttons in fours---Irish Guards5.Buttons in fives --- Welsh Guards

These red jackets, known as "full dress" are the last hangover from the Victorian era.